帶有GUI的簡單Java程序，我的錯誤是什么？

Question

我有下面的代碼（java）

    import java.awt.*;
    import javax.swing.*;
    import java.awt.event.*;
    import java.io.File;

    public class DirectoryIndexer extends JFrame implements ActionListener, MouseListener {

            JPanel OutputPane001 = new JPanel();
            JTextArea OutputTextArea001 = new JTextArea();

            JPanel zeButtonPane = new JPanel();
            JButton zeButton = new JButton("Index This Mess!");
            zeButton.addActionListener(this);

            JPanel InputPane001 = new JPanel();
            JTextField InputTextField001 = new JTextField();

            String[] DirList;
            String DirListConcat = "";


            public DirectoryIndexer() {
                super();
                setSize(750, 550);
                setTitle("920's Second Attempt At A Java Program With A GUI");
                setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                BorderLayout OutputPaneLayout = new BorderLayout();
                OutputPane001.setLayout(OutputPaneLayout);
                OutputTextArea001.setSize(550,435);
                OutputPane001.add(OutputTextArea001);
                OutputPane001.setSize(600,485);
                add(OutputPane001, BorderLayout.WEST);

                BorderLayout zeButtonPaneLayout = new BorderLayout();
                zeButtonPane.setLayout(zeButtonPaneLayout);
                zeButtonPane.add(zeButton);
                zeButtonPane.setSize(120,485);
                add(zeButtonPane, BorderLayout.EAST);

                BorderLayout InputPaneLayout = new BorderLayout();
                InputPane001.setLayout(InputPaneLayout);
                InputPane001.add(InputTextField001);
                InputPane001.setSize(720,20);
                add(InputPane001, BorderLayout.SOUTH);

                setVisible(true);
            }

            public void actionPerformed(ActionEvent event) {
                super();
                string DirToIndex = InputTextField001.getText();
                String files;
                File folder = new File(DirToIndex);
                File[] listOfFiles = folder.listFiles(); 

                for (int i = 0; i < listOfFiles.length; i++) 
                {        
                    if (listOfFiles[i].isFile()) 
                    {
                        files = listOfFiles[i].getName();
                        DirList[i] = files;
                        DirListConcat = DirListConcat + files;
                    }
                }

                OutputTextArea001.setText(DirListConcat);           

            }

            public static void main(String[] arguments) {
                DirectoryIndexer MainFrame = new DirectoryIndexer();
            }


    }

抱歉，如果顯示不正確，當我嘗試發布代碼時，stackoverflow會出現故障...但是無論如何...

我是Java的初學者，嘗試生成一個程序，該程序采用userinput“路徑”，讓用戶按下按鈕，然后轉過身並對該目錄建立索引，然后將輸出打印到此textarea。

我收到以下錯誤：

    cmd /c cd "C:\Users\Charles\custom_java_dir\charles\GUI2" && "javac" "DirectoryIndexer.java"
    Process started >>>
    DirectoryIndexer.java:13: error: <identifier> expected
            zeButton.addActionListener(this);
                                      ^
    DirectoryIndexer.java:13: error: illegal start of type
            zeButton.addActionListener(this);
                                       ^
    2 errors
    <<< Process finished. (Exit code 1)
    cmd /c java DirectoryIndexer
    Process started >>>
    <<< Process finished. (Exit code 0)
    ================ READY ================

Answer 1

您正在嘗試在方法之外發出Java語句。 您可以在方法之外聲明變量，但不能在語句之外聲明變量。

Answer 2

zeButton.addActionListener(this); 在DirectoryIndexer類的變量聲明中，這是不正確的。 您只能從方法內部調用方法。

Answer 3

這種聲明不能在方法之外： zeButton.addActionListener(this);

嘗試將其移至構造函數。